This invention relates to a dead axle which is particularly useful for mounting the wheels beneath a truck drawn trailer and similar vehicles where the axles are not powered nor arranged to turn relative to the direction of movement of the vehicle.
Truck drawn trailers are supported upon wheels which are mounted upon dead axles that are fastened beneath, and extend the width of, the vehicle. The opposite ends of the such axles are formed with spindles or hubs upon which the wheels are mounted. On large vehicles, such as long trailers, where there are a number of axles and a large number of wheels, the axles add considerable weight to the vehicle. Thus, it would be useful to provide a dead axle which, although heavy enough and strong enough to support large loads, is nevertheless relatively light in weight.
Light weight axles and light weight drive shafts have been manufactured in the past by an extrusion process that, in essence, comprises extruding a tubular blank through a die throat by means of a ram or pusher punch. The punch pushes the blank in an axial direction through the die throat Typically, the punch is formed with forward extensions, like mandrels, which are located within the blank and within the die throat during the extrusion of the blank. Thus, depending upon the locations and diameters of the extensions, some portions of the wall thickness of the extruded tube are made thicker than other portions. The different wall thicknesses are produced by the radial dimensions of the annular spaces located between the extensions and the die throat.
The extrusion process may be performed with the blanks at room temperature or heated to facilitate the flow of the blank metal during the extrusion steps. Examples of this form of process for manufacturing light weight axles or drive shafts for vehicles are disclosed in U.S. Pat. No. 4,292,831 issued Oct. 6, 1981 to Joseph A. Simon for xe2x80x9cA process for extruding a metal tube with inwardly thickened portionsxe2x80x9d; U.S. Pat. No. 5, 105,644 issued Apr. 21, 1992 to Joseph A. Simon for a xe2x80x9cLight weight drive shaftxe2x80x9d; U.S. Pat. No. 5,241,848 issued Sep. 7, 1993 to Joseph A. Simon for a xe2x80x9cLight weight drive shaftxe2x80x9d; U.S. Pat. No. 5,320,580 issued Jun. 14, 1994 to Joseph A. Simon for a xe2x80x9cLight weight drive shaftxe2x80x9d; and U.S. Pat. No. 5,522,246 issued Jun. 4, 1996 to Norina A. Simon for a xe2x80x9cProcess for forming light-weight tubular axlesxe2x80x9d.
U.S. Pat. No. 5,522,246 describes a process within which a portion of a light weight axle is formed with an opening that is substantially elliptical in cross section. This produces an area along the length of the axle whose wall thicknesses vary from thick to thin, thereby reducing weight in some of the areas where a greater wall thickness is not needed for strength purposes.
The present invention is concerned with an improved process that is somewhat similar to the previously mentioned processes, but wherein the axle is provided with an elongated central section whose wall thickness varies considerably in cross section, so as to provide greater strengthened longitudinally extending wall segments where needed for high load absorption, and with the opposite ends of the tubular central section attached to separately formed spindles for mounting supporting wheels. The central section may be horizontally oriented to accommodate and absorb high applied loads while the overall weight of the axle may be reduced.
This invention contemplates a dead axle and a method of making a dead axle which comprises an elongated tube which is normally arranged in a horizontal position, spanning the width of a vehicle, such as a trailer or truck-tractor or other such vehicle, upon which wheels may be mounted. The axle is formed, of an elongated extruded tube having a center portion and two opposite end portions. The center portion, has a uniform exterior cross section throughout its length, and an interior opening whose cross-section is asymmetrical relative to the longitudinal axis of the tube. The end portions preferably are formed with circular cross-section openings to provide approximately circular end faces on the opposite ends of the tube.
The asymmetrical interior opening may be formed, in cross section, in different asymmetrical shapes, such as an off-center elliptical or approximately elliptical shape, an asymmetrical elliptical cross sectional shape wherein the opposite minor radii of the elliptical shape are of different lengths to provide different arcs, or an epicycloid or hypocycloid shape or a shape formed of different radii arcs joined end-to-end. Depending upon the cross-sectional shape of the opening, the wall thickness of the central portion of the dead axle, may be varied considerably to provide sufficient strength to support the anticipated loads. By making the wall thickness variable, theoretical, elongated wall segments are formed along the length of the axle which may be oriented to support the anticipated maximum forces that may be applied in pre-determined directions when the axle is mounted beneath the vehicle.
The opposite end portions provide generally circular in cross section, annular faces which are attached to separately formed spindles. The spindles have free spindle or hub ends upon which the wheels are mounted. The annular faces are arranged in face-to-face contact with the respective tube ends and are welded thereto.
The method for making the tubular center portion of the axle, generally comprises first preparing tubular blanks. These blanks are placed within a circular die having a constricted die throat. A ram or pusher punch engages the end of the blank which is remote from the throat and pushes the blank in an axial direction through the throat. The throat is smaller in diameter than the blank, so that the blank is extruded through the throat. The pusher punch or ram is provided with one or more extensions which, like mandrels, extend into the central opening of the tubular blank and are positioned within the die throat during the extrusion. Thus, the space between the exterior surfaces of the extensions and the interior surface of the circular die throat form an annular space through which the tube is extruded.
Preferably, at least one extension is provided with a cross sectional shape that is asymmetrical, such as non-circular, when the particular extension portion is within the confines of the die throat. That forms an asymmetrical shaped opening in the extrusion, relative to the longitudinal axis of the extrusion. The extension may be formed with an additional extension, which is circular in cross section and which, when positioned within the die throat during the extrusion of the blank, forms the opposite, circular ends of the tube. When the tube is fully extruded, it is contemplated that the separately formed spindle ends will be applied against the opposite ends of the tube and welded thereto to form the complete dead axle. In addition, it is contemplated to provide markers within the tube during the extrusion, to enable the user to properly orient the tube thicker and thinner portions relative to the vehicle and the spindles.
A major object of this invention is to provide a lighter weight dead axle which has integral thicker and thinner longitudinally extending wall segments running along its length and with one or more of the thicker segments being formed for absorption of larger loads than the thinner segments. By orienting the axle relative to the amount and direction of anticipated heavy loads, the axle has sufficient strength. Meanwhile, the axle wall is thinner and, therefore, lighter in those areas that are not subjected to the heavy load.
A further object of this invention is to provide a method for forming a dead axle with an extruded major center portion having thicker and thinner longitudinally extending wall segments and opposite spindle ends secured together to enable the formation of lighter weight axle portions between the opposite spindle ends so as to reduce the overall weight of the axle.
Still a further object of this invention is to provide a light weight axle whose major center portion is formed with multiple thicker integral segments, running almost the full length of the axle, for the absorption of anticipated heavy loads that are generally directionally applied.
These and other objects of this invention will become apparent upon reading the following description, of which the attached drawings form a part.